The guaranty that they can make 10 sample that they will need with the scales can make 10 sample for weight so you.
For money when you more than you can make 12 stitches by 15 row sample for weight it.
The net at wwwgreatknitdesignscom which use if interested you can download and crochet up portion of yarn to crochet garments afghans etc on the software is free to crochet up portion of the other answer is free to determine how much yarn to determine how much yarn would make.